On-line and off, one of the biggest challenges publishers wrestle with is colour matching.

All sorts of systems have been devised to make it possible to take the special shade of blue the designer has come up with, reproduce it accurately in a proofing system, and make it reproduce just as accurately when printed.

Some have come down to such simple expedients as having the client turn up at 3.00 am in a print plant to stand over the sheets coming out of the offset printing machine and physically compare them to the proof.

Computerised matching has reduced that one, but the problem has been made worse – not better – by e-publishing. That’s because you can’t know what hardware and settings the file will be viewed on. And they’re all different. The problem’s three fold:

1. Different monitor technologies display colours differently. The technologies produce very different results – put an LED and LCD monitor beside each other on the same desk (like I have) and the LCD will look brown against the LED, no matter how it’s set.

2. Colour settings vary within the same make and model of hardware. You might set a colour so it looks right on your monitor, but you don’t know how somebody else has set it.

There’s no answer to this. But there are tricks to keep your material internally consistent, including across a series of book covers, for instance – even if the colours you see on your monitor aren’t those seen by somebody with a different system.

Here’s the trick. Reduce it to numbers. Each of the three components in RGB monitor colours is divided into 255 levels, from 0 (off) to 255 (full). Any colour can be defined as a value, for instance R 255, G 0, B 0 gives you bright red. R 85 G 67 and B 4 is mud. And so on. Most of the colour wheels or gradient-selectors that pop up in Word and other packages also show the colour as a numeric value in RGB.

Pick a number – and stick with it.

This isn’t the only available system – others include HSB, CMYK and LAB, though not all software has this built in. Some software, such as Photoshop, has all this and more – including pre-defined libraries of colours using the Pantone PMS matching system, which is the print industry standard.

See what I’m getting at? If you define the colours you want by numeric value – and keep a note of the values – you can reproduce them every time, consistently. And you don’t need to care how they might vary between your screen and somebody else’s, because it’ll be consistent for whatever device is being used to generate them.

When it comes to printing out, of course, there are other steps and cautions. But more of that anon.

It’s one of the trickiest challenges faced by publishers. I recall one story I heard in which a publisher kept tweaking the colours so they looked right on his particular monitor, then sent the file away for printing – only to discover that the monitor colours bore no relation to the way the colours appeared on paper. Oops…

There is a real art to it. I’ve had experiences where some of my photos came out in a printed book with purple sky. I was not involved with any of the colour matching but it was obvious nobody had checked. It’s a specific issue when printing deep blue in cmyk.